This invention is related to apparatus for forming a gear for a double enveloping worm gear drive, and more specifically apparatus for milling bronze gear for such a drive.
A double enveloping worm gear drive employs what is commonly referred to as an "hour-glass" type enveloping worm and a throated gear which tend to wrap around each other to produce a drive. The gear teeth are straight sided, with flanks tangent to the gear base circle. Such a drive is useful because it produces an area contact, rather than the line contact of other worm gear drives. It is often known as a Cone drive, after the name of the inventor. Such gears are conventionaly made by employing an enveloping hob to semi-finish cut the gear. The gear is initially pre-cut slightly over-sized. The hob is then side-fed against either flank to finish to the desired tooth thickness.